Crimped Polyamide Conductive Filament, Manufacturing Method and Application Thereof

ABSTRACT

The present invention relates to a crimped polyamide conductive filament, a manufacturing method and an application thereof. The crimped polyamide conductive filament is obtained by subjecting a conductive fiber with composite structure prepared by melt composite spinning process to a crimping deformation process, and has a crimp shrinkage of 15%-60% and a crimp stability of 40%-90%. The process of deformation processing is as follows: the conductive fiber protofilament is heated and plasticized by a deformed hot-box, cooled by a cooling plate, twisted and untwisted by a false twister, shaped, added with interlaced nodes, oiled, wound, inspected, and packaged. The crimped polyamide conductive filament is beneficial to the subsequent blended weaving, or used alone for weaving, and can exhibit a soft human experience effect, and can be widely used in intelligent sensing, smart wear and other fields.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims priority to Chinese Patent Application No. 201710772323.6, filed on 31 Aug., 2017, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a crimped polyamide conductive filament, manufacturing method and application thereof, belonging to the technical field of conductive fibers.

BACKGROUND

Currently available conductive filaments have straight and smooth surface, and have small cohesion force. When these conductive filaments are combined with other fibers, they are prone to cause looped yarns and disadvantageous for the processing of the conductive fiber fabric. If the conductive filament is used alone in the weaving process, the fiber gets hard and the wearability of fiber is not good. If the conductive filament is woven into a sock, the conductive layer may partially fall off after being under pressure for a long time, affecting the electrical conductivity and the flow of current. At present, there are no crimped polyamide conductive filament products.

Patent application CN106758179A discloses a silver plating method for polyamide DTY fibers. After performing the chemical silver plating on polyamide POY fiber, the obtained conductive antibacterial fiber is subjected to elasticity enhancing process (crimping deformation process) to obtain polyamide silver-plated DTY fiber. Patent application CN102560729A discloses an antibacterial and moisture-conductive type polyester fiber, a preparation method and application thereof. A silver-based antibacterial masterbatch and polyester chip molten mixed spinning, as well as a special-shaped spinneret plate are used to obtain the special-shaped antibacterial polyester pre-orientated yarns. After enhancing elasticity, the low-elastic special-shaped polyester antibacterial fiber is obtained, which has good wearability. Patent application CN105887240A discloses polyester pre-oriented yarns and a preparation method thereof, polyester fiber fabrics and preparation method thereof. Polyester pre-oriented yarns spun with silver-based antibacterial masterbatch and water-soluble polyester is used, after subjected to elasticity enhancing processing (crimping deformation treatment), the polyester high-elastic yarns are obtained and woven into fabrics; thereafter, the fabrics are dissolved to remove the water-soluble polyester portion, and vacuum-plated with silver to obtain antibacterial and conductive fabrics. Patent CN102953137B discloses a highly elastic conductive fiber and a preparation method thereof. Carbon nanotubes are dispersed in ionic liquid, and then mixed with a highly elastic thermoplastic polymer to be melt-spun to obtain a highly elastic fiber containing carbon nanotubes.

None of the above-disclosed patent applications relates to a crimping deformation process for a conductive fiber having a composite structure.

In recent years, due to the development of electronic technology and life sciences, smart wear and fiber-type biosensors have become popular, in-demand fields of the technology applications and consumer markets. The demand for conductive fabrics is increasing, and higher requirements are raised on the softness and wearability of conductive fabrics. The conductive fibers having composite structures are relatively easy to produce and manufacture and easy to control the production cost because of its good electrical conductivity. With the expansion of the application of smart wear and fiber-type biosensor, this industry will be greatly developed.

SUMMARY

The objective of the present invention is to overcome the deficiencies in the prior art, and to provide a crimped polyamide conductive filament, a manufacturing method and an application thereof. It solves the problems of having insufficient cohesive force when the conductive fiber product is combined with other fibers, the occurrence of looped yarns thereby affecting the fabric processing, and the problem where woven fabric gets hard and has poor wearability when the conductive fiber product is used alone for the weaving process.

According to the technical solution provided by the present invention, a crimped polyamide conductive filament is obtained by subjecting a polyamide conductive filament to a crimping deformation process, and the crimped polyamide conductive filament has a crimp shrinkage of 15%-60% and a crimp stability of 40%-90%.

Further, the polyamide conductive filament is composed of a conductive portion and a non-conductive portion, and the conductive portion accounts for 10%-40% of the total amount of the conductive filament; the polyamide conductive filament has a sheath-core structure, and the sheath layer is the conductive portion; or, the polyamide conductive filament has a composite structure, and the conductive portion is embedded in the non-conductive portion and the conductive portion is partially exposed on the surface of the polyamide conductive filament.

Further, the conductive portion is composed of a conductive agent, a processing aid and a polyamide carrier, and the conductive agent is a conductive carbon black with an additive amount of 20%-35%, or a carbon nanotube with an additive amount of 5%-15%, or a composite conductive agent composed of conductive carbon black and carbon nanotubes and having an additive amount of 10%-25%, or a light-colored conductive metal oxide with an additive amount of 50%-80%.

Further, the light-colored conductive metal oxide is an antimony-doped titanium dioxide conductive powder.

Further, the crimped polyamide conductive filament has a monofilament fineness of 1.5-6 dtex, a strength of 2.0-3.5 cN/dtex, an elongation of 15%-35%, a resistivity of 10⁰-10² Ω·cm, and a surface resistance of 10²-10⁵Ω.

The method for manufacturing the crimped polyamide conductive filament includes the following process steps.

The polyamide conductive filaments are sequentially subjected to the steps of heating and plasticizing, cooling, false-twisting, shaping, adding interlaced nodes, oiling and winding. The temperature of the heating and plasticizing is 145-195° C., the shaping temperature is 25-135° C., the draft multiple is 1.05-1.5, the value of D/Y is 1.6-2.5, and the winding speed is 100-800 m/min.

The crimped polyamide conductive filament is used for preparing antistatic and radiation resistant fabrics, fiber fabric type sensors, and smart wearable products.

The present invention has the following beneficial effects:

(1) when double-twisted and interlace processed with polyamide low-elastic yarn, or polyamide fully drawn yarn (FDY), the polyamide conductive filaments treated by a crimping deformation process have a good cohesive force, and looped yarns, ear silk and other situations affecting the subsequent weaving can be avoided;

(2) fabrics obtained by directly performing a weaving process on the polyamide conductive filaments treated by a crimping deformation process have soft hand feel and good wearability on the premise of maintaining its original good electrical conductivity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a sheath-core structure of a crimped polyamide conductive filament.

FIG. 2 is a schematic diagram of a composite structure of a crimped polyamide conductive filament.

DESCRIPTION OF THE REFERENCE NUMBERS

1—conductive portion, 2—non-conductive portion

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention will be further described below with reference to the specific drawings and embodiments.

In the present invention, the polyamide conductive filaments prepared by a melt composite spinning process, which is used for the crimping deformation process, are composed of a non-conductive portion made of a fiber-forming polyamide polymer, and a conductive portion having a conductive agent made of conductive carbon black, carbon nanotubes, a composite of the conductive carbon black and the carbon nanotubes, or conductive metal oxide powder, and are formed by a composite spinning process. The conductive portion is composed of a fiber-forming polyamide polymer, a conductive agent and an auxiliary agent.

The fiber-forming polyamide polymer may be an aliphatic polyamide and a copolymer thereof, such as polyamide 6, polyamide 66, polyamide 610, polyamide 10, polyamide 12, or polyamide 612; an alicyclic polyamide; and an aromatic polyamide. These fiber-forming polymers can be used individually or in combination as appropriate.

The typical preparation method of the conductive fiber protofilament is described as below.

(1) Conductive masterbatch: the conductive agent or the composite conductive agent, the auxiliary agent and the fiber-forming polymer slice are pre-kneaded, and then subjected to the twin-screw melt blending, extrusion, water cooling and pelletizing to obtain the conductive masterbatch. Wherein, if the fiber is black, the conductive agent is the conductive carbon black with an additive amount of 20%-35%, or the carbon nanotube with an additive amount of 5%-15%, or the composite conductive agent composed of conductive carbon black and carbon nanotube and having an additive amount of 10%-25%; if the fiber is light color to white, the conductive agent is a light-colored conductive metal oxide such as antimony-doped titanium dioxide conductive powder, and the additive amount of the light-colored conductive metal oxide is 50%-80%.

(2) Composite spinning: the fiber-forming polymer slices and the conductive masterbatch are respectively melt-conveyed by a screw extruder, and are metered and distributed to the respective spinneret orifices of the composite spinneret plate by a metering pump, and are then ejected from the spinneret orifices, and finally subjected to side blowing, cooling and solidification, drafting, oiling, guiding wire and winding;

the non-conductive portion slices used therein are previously dried, the water content thereof is controlled to be less than 50 ppm, and the drying process can be achieved by fluidized bed drying, drum drying, continuous drying in a nitrogen atmosphere, etc.;

the conductive masterbatch is previously dried, and the water content is controlled to be less than 100 ppm.

In the step (1), the kneading temperature is 80-140° C., and the time is 30-120 min; the temperatures of the twin-screw melt blending and extrusion are determined according to the melting point of the fiber-forming polymer, for example, for a polyamide polymer having a melting point of 220° C., the temperature in the first zone is set to 80-100° C., 200° C. in the second zone, and the temperature in each zone from the third zone to the extrusion port is 250-270° C.; and the slenderness ratio of the screw is 1:25-1:50.

In the step (2), the temperature of the screw extruder in the spinning process is set as long as it can make the polymer melt-conveyed normally and achieve a certain apparent viscosity. It should be specially noted that for the composite spinning, the similar apparent viscosity of the two types of spinning melts is essential for the normal operation of the spinning, and the process of the different fiber-forming polymers should be carefully explored and then the apparent viscosity is determined.

In the step (2), the process parameters of the filament cooling medium include the wind pressure, the wind speed, the wind temperature, and the wind humidity of the side blowing. The draft winding speed is generally 2,000-5,000 m/min, and the drafting can be carried out using a hot-box or a hot roller.

The performance indexes of typical carbon black sheath-core polyamide conductive fiber protofilament are: (1) the fineness is 44 dtex, the monofilament fineness is 3.7 dtex; (2) the strength is 2.5 cN/dtex; (3) the elongation is 55%; (4) the resistivity is 65 Ω·cm; (5) the surface resistance is 10⁴Ω.

The conductive fiber protofilament is subjected to crimping deformation process using a texturing machine, and the key points of adjustment of the process conditions and process parameters are described as follows:

The process conditions are mainly yarn speed (YS), draw ratio (DR), speed ratio (D/Y, which refers to the ratio of the surface speed of the friction disk to the speed at which the yarn leaves the false twister), K value (ratio of untwisting tension to twisting tension), overfeed rate, and two hot-box temperatures.

(1) Hot-box temperature and cooling plate: the temperature of the first hot-box is the deformation temperature of the fiber. The setting requirement is that the fiber can be plasticized but cannot be adhered. The second hot-box is also called a shaping hot-box, which is a non-contact type air heating, generally heated by a heat medium. The function of the second hot-box is to shape the false-twisted yarn, but the high temperature will also cause a decrease in the crimp rate (elasticity) of the yarn.

(2) Draw ratio and speed (overfeed rate): the draw ratio is the ratio of the speed of the second roller to that of the first roller. The general calculation of the draw ratio is estimated based on the fineness of the protofilament or the fineness of the processed filament, and the fineness of the protofilament or the fineness of the processed filament is used as the basis for process adjustment. With the increase of the draw ratio, the strength of the yarn increases and the elongation of the yarn decreases.

The yarn speed has great influence on the tension, crimp shrinkage, crimp stability and whether it is easy to appear the broken filaments, ossified filaments, etc., and the best process parameters should be carefully adjusted to produce satisfactory products.

(3) K value and D/Y ratio: the D/Y ratio refers to the ratio of the surface speed of the friction disk to the speed at which the yarn leaves the false twister. Within a certain range, the change of D/Y ratio has almost no effect on the physical indexes such as crimp shrinkage, crimp stability, strength and elongation of the fiber, and the change of D/Y ratio is only related to the tension of the false twister before and after the processing. Unsatisfactory process parameters can lead to tight spots or broken filaments, which is not conducive to stable production.

For the crimping deformation process of the carbon black composite structure conductive fiber of the present invention, the generally optimized process parameters are: temperature of the heating and plasticizing is 145-195° C., the shaping temperature is 25-135° C., the draft multiple is 1.05-1.5, the value of D/Y is 1.5-2.5, and the winding speed is 100-800 m/min.

The application of the crimped polyamide conductive filament of the present invention is roughly classified into two types: a woven or nonwoven material directly made from it, and a fibrous functional material body obtained by doubling, double-twisting and re-weaving the crimped polyamide conductive filament with a raw material fiber of the non-conductive fiber. The applications of the crimped polyamide conductive filaments of the present invention in the preparation of antistatic and radiation resistant fabrics, fiber fabric type sensors, and smart wearable products are all within the protective scope of the present invention.

The present invention performs a crimping deformation treatment on the conductive fiber protofilament obtained by the composite spinning process, so that the crimped polyamide conductive fiber, the conductive yarn of the present invention and the products manufactured thereby have the following characteristics, such as excellent electrical conductivity, thermogenesis, antistatic property, electromagnetic wave and magnetic shielding properties, and thermal conductivity. Further, it has good processability and comfortable wearability. In addition, the conductive fiber, the conductive yarn and the extended products thereof have excellent durability of the above various characteristics, and also have the following characteristics such as excellent softness and touch (or texture), easier for treating, and excellent processability. Therefore, by flexibly using the above characteristics as much as possible, the conductive fiber, the conductive yarn and their products can be effectively used in various applications, for example, the applications of making the clothing having antistatic property or electromagnetic wave and magnetic shielding properties (e.g., work clothes or uniforms), interior decoration applications (e.g., curtains, carpets, wall covering materials, and partitions), and the applications of making the neutralization bag filters, instrument covers, copier brushes and electromagnetic shielding industrial materials. Furthermore, according to the manufacturing method of the present invention, the crimped polyamide conductive filament, the conductive yarn, and the extended products thereof can be smoothly produced, and the manufacturing method has excellent practicability.

The present invention will be further described in detail with reference to the specific embodiments.

Embodiment 1: Crimping Deformation Process of Polyamide Conductive Filaments

The polyamide conductive filament is a composite structure including a conductive portion and a non-conductive portion, and the conductive portion is embedded in the non-conductive portion in a trilobal shape, the fineness is 110 dtex/32 f, the strength is 1.8 cN/dtex, the elongation is 105%, the high-voltage resistance is 5×10⁶ Ω/cm, and the surface resistance is 10⁵Ω. The parameters of the crimping deformation process are: the temperature of first hot-box is 170° C., the draft multiple is 1.25, D/Y is 1.8, the temperature of second hot-box is 125° C., the assembly form of friction disc is 3-5-1, the shaping underfeed is −7.5%, the winding underfeed is −4.5%, and the yarn speed is 380 m/min.

The fiber indexes of the obtained crimped polyamide conductive filament are: the fineness is 90 dtex/32 f, the strength is 3.0 cN/dtex, the elongation is 25%, the crimp shrinkage is 22%, the crimp stability is 75%, the oil content is 2.5%, the boiling water shrinkage is 4.5%, the high-voltage resistance is 2×10⁶ Ω/cm, and the surface resistance is 10⁵Ω.

Embodiment 2: Crimping Deformation Process of Polyamide Conductive Filaments

The polyamide conductive filament is a carbon black sheath-core polyamide conductive fiber, the fineness is 83 dtex/16 f, the strength is 2.5 cN/dtex, the elongation is 55%, the high-voltage resistance is 1.5×10⁶ Ω/cm, and the surface resistance is 10³Ω. The parameters of the crimping deformation process are: the temperature of first hot-box is 175° C., the draft multiple is 1.05, D/Y is 1.9, the second hot-box is closed or not equipped, the assembly form of friction disc is 3-5-1, the shaping underfeed is −7.5%, the winding underfeed is −4.5%, and the yarn speed is 500 m/min.

The fiber indexes of the obtained carbon black sheath-core crimped polyamide conductive filament are: the fineness is 80 dtex/16 f, the strength is 2.8 cN/dtex, the elongation is 30%, the crimp shrinkage is 45%, the crimp stability is 71%, the oil content is 2.5%, the boiling water shrinkage is 6.5%, the high-voltage resistance is 8.5×10⁵ Ω/cm, and the surface resistance is 10³Ω.

Embodiment 3: Low or No Torque Plying Processing of the Crimped Polyamide Conductive Filament

The conductive protofilament is a carbon black sheath-core polyamide conductive fiber, the fineness is 83 dtex/16 f, the strength is 2.5 cN/dtex, the elongation is 60%, the high-voltage resistance is 1.5×10⁶ Ω/cm, and the surface resistance is 10⁴Ω. The parameters of the crimping deformation process are: the deformation temperature is 170° C., the draft multiple is 1.2, D/Y is 1.9. The two conductive filaments are doubled after going through a false twister in a Z-twist direction and in an S-twist direction, respectively, the shaping underfeed is −6.8%, the winding underfeed is −3.1%, and the yarn speed is 450 m/min.

The fiber indexes of the obtained carbon black sheath-core crimped polyamide conductive filament are: the fineness is 145 dtex/32 f, the strength is 3.1 cN/dtex, the elongation is 28%, the crimp shrinkage is 42%, the crimp stability is 75%, the oil content is 3.0%, the boiling water shrinkage is 6.5%, the high-voltage resistance is 8.5×10⁵ Ω/cm, and the surface resistance is 10⁴Ω, basically no torque.

Embodiment 4: Doubling and Interlace Processing of the Crimped Polyamide Conductive Filaments with the Polyamide FDY

The raw materials of the doubling processing include: 20 D/4 f crimped polyamide conductive filaments; 50 D/24 f polyamide FDY.

Method: performing the doubling on the two raw materials, and adding interlaced nodes to obtain 20 D/4 f+50 D/24 f polyamide composite conductive interlaced yarns.

Result: there is no looped yarns on the bobbin, and it has favorable effects.

Embodiment 5: Crimped Polyamide Conductive Filament Hosiery

The 80 dtex/16 f carbon black sheath-core crimped polyamide conductive filament obtained in Embodiment 2 were woven into a 50 cm sock with a hosiery machine. The appearance is visible, the fabric is neat and beautiful, it feels soft in the hand, and the surface resistance tested by a surface resistance tester is 10³Ω. After washing 30 times with water and washing liquid, the surface resistance only slightly decreased to 10³⁻⁴Ω.

Comparative Example 1 Doubling and Interlace Processing of the Conductive Fibers with the Polyamide FDY

The raw materials of the doubling processing include: conductive fibers: 20 D/4 f Polyamide Conductive Filaments; 50 D/24 f polyamide FDY.

Method: performing the doubling on the two raw materials, and adding interlaced nodes to obtain 20 D/4 f+50 D/24 f polyamide composite conductive interlaced yarns.

Result: it is easy for the ear silk to appear on the bobbin, and the effect is not ideal.

Comparative Example 2 Conductive Fiber Hosiery

The 83 dtex/16 f polyamide conductive fiber protofilament of Embodiment 2 was directly woven into a 50 cm sock with a hosiery machine. The appearance is visible, the fabric is rough, and feels hard in the hand, and the surface resistance tested by a surface resistance tester is 10³Ω. After washing 30 times with water and washing liquid, the surface resistance decreased significantly to 10⁴⁻⁵Ω. 

What is claimed is:
 1. A crimped polyamide conductive filament, wherein the crimped polyamide conductive filament is obtained by subjecting a polyamide conductive filament to a crimping deformation process, a crimp shrinkage of the crimped polyamide conductive filament is 15%-60%, and a crimp stability of the crimped polyamide conductive filament is 40%-90%.
 2. The crimped polyamide conductive filament according to claim 1, wherein the polyamide conductive filament is composed of a conductive portion and a non-conductive portion, and the conductive portion accounts for 10%-40% of a total amount of the polyamide conductive filament; the polyamide conductive filament has a sheath-core structure, and a sheath layer is the conductive portion; or, the polyamide conductive filament has a composite structure, the conductive portion is embedded in the non-conductive portion and the conductive portion is partially exposed on a surface of the polyamide conductive filament.
 3. The crimped polyamide conductive filament according to claim 2, wherein the conductive portion is composed of a conductive agent, a processing aid and a polyamide carrier, and the conductive agent is a conductive carbon black with an additive amount of 20%-35%, a carbon nanotube with an additive amount of 5%-15%, a composite conductive agent composed of the conductive carbon black and the carbon nanotubes and having an additive amount of 10%-25%, or a light-colored conductive metal oxide with an additive amount of 50%-80%.
 4. The crimped polyamide conductive filament according to claim 3, wherein the light-colored conductive metal oxide is an antimony-doped titanium dioxide conductive powder.
 5. The crimped polyamide conductive filament according to claim 1, wherein the crimped polyamide conductive filament has a monofilament fineness of 1.5-6 dtex, a strength of 2.0-3.5 cN/dtex, an elongation of 15%-35%, a resistivity of 10⁰-10² Ω·cm, and a surface resistance of 10²-10⁵Ω.
 6. A method for manufacturing a crimped polyamide conductive filament, wherein the method comprises the following process steps: a polyamide conductive filament is sequentially subjected to the steps of heating and plasticizing, cooling, false-twisting, shaping, adding interlaced nodes, oiling and winding; a temperature of the heating and plasticizing is 145-195° C., a shaping temperature is 25-135° C., a draft multiple is 1.05-1.5, a value of D/Y is 1.6-2.5, and a winding speed is 100-800 m/min.
 7. A crimped polyamide conductive filament containing as an essential material in products selected from the group consisting of antistatic and radiation resistant fabrics, fiber fabric type sensors, and smart wearable products. 